1. Technical Field
The present invention—in machine tools furnished with a plurality of structures including at least tool-and workpiece-holding structures, and furnished with drive mechanisms for driving structures, among the plurality of structures, that are equipped to be movable, and with a controller for controlling the drive mechanisms based on a machining program—relates to interference-checking devices that check whether movement by the movable structures will cause the moving structures themselves, the other structures apart from the moving structures, or the tools or the workpieces to interfere with each other.
2. Description of the Related Art
A lathe, which is one type of machine tool, comprises a plurality of structures, namely a bed, headstock, spindle, saddle, tool rest and tailstock, along with feed mechanisms that let the saddle, tool rest and tailstock travel, with the tool held in the tool rest and the workpiece held by the spindle. In addition, a machining center comprises a plurality of structures, namely a bed, column, spindle head, spindle, saddle and table, along with feed mechanisms that let the column, spindle head, saddle and table travel, with the tool held in the spindle and the workpiece held on the table. Moreover, the feed mechanisms are controlled by a controller so that their operation is appropriately controlled according to a machining program.
This machining program is written according to the design for the shape of the workpiece, and after being written, the program is checked for errors before the actual machining. If errors are present, that portion is revised, and if no errors are present, the machining program is used to perform continuous machining. This advance check of the machining program is done in this manner because, if such errors are present, there is a risk of serious accidents involving the tool, workpiece or other structures interfering with each other.
Moreover, this check (interference check) is conventionally performed by operating the machine tool, and running the machining program being checked in a trial operation mode that does not involve machining of the workpiece, and having the operator check the direction of feed of the tool as appropriately displayed on an image display device (see JP H2-59256A).
Specifically, the controller for the machine tool performs a sequential analysis of each block of the machining program, recognizes the travel position and feedrate of the tool, and calculates the direction of travel, amount of travel and method of travel (cutting feed or rapid feed) of the tool based on the travel position and feedrate thus recognized. Thereafter, based on the direction of travel and amount of travel thus calculated, these are displayed as vectors on the image display device, and the method of travel is indicated by means of the display color (white in the case of cutting feed and red in the case of rapid feed). Note that in the analysis of the machining program, a block ahead of (succeeding) the block being executed in order to control the travel of the tool is analyzed, and thus the future direction of travel and method of travel of the tool are displayed sequentially on the image display device.
Then, the operator checks the display screen thus displayed, determines the direction of travel, amount of travel and method of travel of the tool, and checks to see if any of this will interfere with the workpiece (thus checking for errors in the machining program).
However, in the conventional example described above, the direction of travel, amount of travel and method of travel of the tool are displayed with vectors and there is a problem in that this display alone is not sufficient for the operator to accurately predict the positional relationships between the tool and workpiece after travel, and as a result, the operator cannot accurately determine whether interference is present or not.
Moreover, interference may occur in a machine tool not only between the tool and workpiece, but rather, for example, the tool rest may interfere with another structure during its travel, or when the spindle is indexed so that the workpiece rotating about its central axis comes to a predetermined angular position of rotation, the workpiece may interfere with the tool or another structure, so there is a possibility of other types of interference arising between the tool or workpiece and a structure or between structures, and these interfering relationships cannot be checked in the conventional example described above.
In this manner, in the conventional example described above, not all of the interfering relationships that could possibly occur in a machining tool can be checked accurately and efficiently.